Brushless motor

Abstract

To provide a brushless motor in which a rotation angle detection accuracy with a magnetic sensor is improved, and a member for supporting a magnetic induction member becomes unnecessary.SOLUTION: A rotor 40 comprises a rotor core 41, and a plurality of rotor magnets 48 constituting a plurality of magnetic poles with alternating polarities in a circumferential direction of the rotor core 41. The rotor 40 is made to rotate with a shaft 14 as a center by a rotating magnetic field generated via current application to a coil 26. A magnetic sensor 31 is provided on a substrate 33 fixed to a stator 20 at a position separated from an end face of the rotor core 41 in an axial direction of the rotor 40, and detects a rotation angle of the rotor 40 based on a change in magnetism of the rotor magnet 48. A magnetic induction member 501 has: a bottom part 52 coming into contact with the end face of the rotor core 41; and an axial direction extension part 55p erected toward the magnetic sensor 31 from the bottom part 52. The magnetic induction member 501 guides the magnetism of the rotor magnet 48 to the magnetic sensor 31.SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] The present invention relates to a brushless motor.

Background Art

[0002] Conventionally, a brushless motor that detects the rotation angle by detecting the magnetic change of the rotor magnet accompanying the rotation of the motor with a magnetic sensor is known.

[0003] For example, the brushless motor disclosed in Patent Document 1 includes a rod-shaped magnetic induction member that extends from the rotor magnet side to the magnetic sensor side and guides the magnetism generated from the rotor magnet to the magnetic sensor mounted on the substrate.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the brushless motor of Patent Document 1, the rod-shaped magnetic induction member is arranged so as to overlap the coil of the stator in the radial direction of the rotor. Therefore, there is a problem that the induced magnetism is affected by the magnetic field generated when the coil is energized, and the rotation angle detection accuracy is reduced. In addition, since a separate member for supporting the magnetic induction member is required, the number of parts increases and the cost increases.

[0006] The present invention has been created in view of such points, and an object thereof is to provide a brushless motor in which the rotation angle detection accuracy by a magnetic sensor is improved and a member for supporting a magnetic induction member is unnecessary.

Means for Solving the Problems

[0007] The brushless motor according to the present invention includes a stator (20), a rotor (40), one or more magnetic sensors (31, 32), and magnetic induction members (501 to 508). The stator has coils (26) wound around a plurality of teeth (24) arranged in the circumferential direction, and slots (25) are formed between adjacent teeth.

[0008] The rotor has a rotor core (41) and a plurality of rotor magnets (48) that form a plurality of magnetic poles with alternating polarities in the circumferential direction of the rotor core. The rotor rotates about a shaft (14) by a rotating magnetic field generated by energizing the coils.

[0009] The magnetic sensors are provided on a substrate (33) fixed to the stator at a position axially away from the end face of the rotor core, and detect the rotation angle of the rotor based on changes in the magnetism of the rotor magnets.

[0010] The magnetic induction members have a bottom portion (52) that abuts against the end face of the rotor core and axially extending portions (55p, 55c) that stand upright from the bottom portion toward the magnetic sensors. The magnetic induction members induce the magnetism of the rotor magnets to the magnetic sensors.

[0011] In the present invention, since the axially extending portions of the magnetic induction members are arranged away from the stator in the radial direction of the rotor, they are less affected by the magnetic field generated when the coils are energized. Therefore, the rotation angle detection accuracy by the magnetic sensors is improved. Further, since the bottom portion of the magnetic induction member abuts against and is fixed to the end face of the rotor core, a separate member for supporting the magnetic induction member is not required, and the number of parts and cost are reduced.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

Figure 15

Figure 16

Mode for Carrying Out the Invention

[0013] Multiple embodiments of the brushless motor will be described with reference to the drawings. "The present embodiment" includes the following first to sixth embodiments. The brushless motor of the present embodiment is applied to vehicle auxiliary equipment and the like, and the rotation angle is detected by a magnetic sensor.

[0014] (First Embodiment) Referring to FIGS. 1 to 6, the configuration, operation, and effects of the brushless motor 101 according to the first embodiment will be described. First, referring to FIGS. 1 and 2, the overall configuration of the brushless motor 101 will be described. FIG. 1 shows an axial cross-section of the brushless motor 101. Assuming that the upper side of the paper surface of FIG. 1 is defined as the top, FIG. 1 shows only the upper part of the axial cross-section and omits the lower part. FIG. 2 corresponds to the cross-sectional view of FIG. 1. In this specification, the following figures similar to FIGS. 2 and 3 are regarded as plan views viewed from above the end face of the rotor 40 and are referred to as "schematic plan views".

[0015] The brushless motor 101 is an inner-rotor type motor including a stator 20 and a rotor 40 that rotates about a shaft 14 inside the stator 20 in the radial direction. The outer shell of the brushless motor 101 is composed of an upper plate 11 and a cylindrical case 12. A bearing 13 fixed to the upper plate 11 rotatably supports the upper part of the shaft 14. Note that the lower part of the shaft 14 is rotatably supported by another bearing (not shown).

[0016] The stator 20 and the rotor 40 are provided coaxially with respect to the rotation axis O of the shaft 14. The outer wall of the stator 20 is fixed to the inner wall of the case 12. The rotor 40 is fixed to the shaft 14 and rotates integrally with the shaft 14. A substrate 33 on which elements for controlling the drive of the brushless motor 101 are mounted is fixed to, for example, the lower surface of the upper plate 11. Therefore, the substrate 33 is indirectly fixed to the stator 20.

[0017] The stator core 21 of the stator 20 has an annular back yoke 23 and a plurality of teeth 24 arranged in the circumferential direction and protruding radially inward from the back yoke 23. The stator core 21 is formed by laminating, for example, thin plate-shaped magnetic steel sheets. The stator 20 is formed by winding coils 26 around the plurality of teeth 24. Slots 25 are formed between adjacent teeth 24.

[0018] The stator 20 of the present embodiment has 12 teeth 24, and 12 slots 25 are formed between the respective teeth. A three-phase current is applied to the coil 26 of the stator 20. That is, four sets of three teeth 24 wound with three-phase windings of U-phase, V-phase, and W-phase are provided in the circumferential direction.

[0019] The rotor 40 has a rotor core 41 and a plurality of rotor magnets 48 that form a plurality of magnetic poles with alternating polarities in the circumferential direction of the rotor core 41. The rotor core 41 is formed by laminating, for example, thin plate-shaped magnetic steel sheets. An air gap δ is provided between the outer wall of the rotor core 41 and the inner wall of the tip of the tooth 24. The rotor 40 rotates about the shaft 14 by a rotating magnetic field generated by energizing the coil 26.

[0020] Specifically, the rotor 40 has an IPM structure in which rectangular parallelepiped rotor magnets 48 are embedded in the square holes of the rotor core 41. A salient pole portion 44 is formed between the rotor magnets 48 adjacent in the circumferential direction. The rotor 40 of the present embodiment has eight rotor magnets 48. That is, the brushless motor 101 illustrated in the present embodiment is an IPM motor of "8 poles (4 pole pairs) 12 slots".

[0021] The brushless motor 101 also includes one or more magnetic sensors 31 provided on the substrate 33. Shown in FIG. 1 is the first magnetic sensor 31. However, basically two magnetic sensors 31 and 32 are provided in the present embodiment as will be described later with reference to FIG. 5. The substrate 33 is fixed to the stator 20 at a position axially away from the end face of the rotor core 41 with respect to the rotor 40. The magnetic sensors 31 and 32 detect the rotation angle of the rotor 40 based on the change in magnetism of the rotor magnet 48.

[0022] Specifically, each of the magnetic sensors 31 and 32 outputs a sensor signal having a sine wave of one cycle as a fundamental wave for each pair of magnetic poles to a signal processing device such as a microcomputer. The signal processing device calculates the rotation angle of the rotor 40 based on the sensor signals of the magnetic sensors 31 and 32. However, if the magnetic sensors 31 and 32 cannot sufficiently detect the magnetism of the rotor magnet 48, the rotation angle detection accuracy decreases. Therefore, the brushless motor 101 includes a magnetic induction member 501 that induces the magnetism of the rotor magnet 48 to the magnetic sensors 31 and 32.

[0023] Incidentally, a magnetic induction member that induces magnetism to a magnetic sensor is disclosed in Patent Document 1 (Japanese Patent Application Laid-Open No. 2017-143727). However, in the prior art of Patent Document 1, a rod-shaped magnetic induction member is arranged so as to overlap the coil of the stator in the radial direction of the rotor. Therefore, there is a problem that the induced magnetism is affected by the magnetic field generated when the coil is energized, and the rotation angle detection accuracy decreases. In addition, since a separate member for supporting the magnetic induction member is required, the number of parts increases and the cost increases.

[0024] Therefore, in the present embodiment, the magnetic sensors 31 and 32 are configured to be less affected by the magnetic field generated when the coil 26 is energized, thereby improving the rotation angle detection accuracy. In addition, by eliminating the need for a member that supports the magnetic induction member 501, the number of parts and the cost are reduced. As a configuration for that purpose, the magnetic induction member 501 has a bottom portion 52 and an axially extending portion 55p.

[0025] Subsequently, referring to FIGS. 3 to 6, the detailed configuration and operation and effects of the magnetic induction member 501 will be described. FIG. 3 shows a schematic plan view of a range of a mechanical angle of 90° corresponding to part III of FIG. 2. In the second to sixth embodiments, the format of FIG. 3 is adopted. FIG. 4 shows a circumferential development view in the viewing direction IV of FIG. 3.

[0026] The magnetic induction member 501 has a bottom portion 52 that abuts against the end face 42 of the rotor core 41, and an axially extending portion 55p that stands upright from the bottom portion 52 toward the magnetic sensors 31 and 32. A part of the magnetism of the rotor magnet 48 propagates directly through the air toward the magnetic sensors 31 and 32, and another part is induced in the axially extending portion 55p and propagates from the tip of the axially extending portion 55p to the magnetic sensors 31 and 32.

[0027] The bottom portion 52 and the axially extending portion 55p are made of a material such as a magnetic steel plate and are integrally formed by, for example, press working. A hole having an inner diameter that fits by interference fit to the outer diameter of the shaft 14 is provided at the center of the bottom portion 52. By press-fitting the central hole of the bottom portion 52 into the shaft 14, the magnetic induction member 501 is fixed to the rotor core 41. In other embodiments, the magnetic induction member 501 may be fixed to the rotor core 41 not only by press-fitting into the shaft 14 but also by caulking or the like to the end face 42 of the rotor core 41.

[0028] In the present embodiment, since the axially extending portion 559 of the magnetic induction member 501 is arranged away from the stator 20 in the radial direction of the rotor 40, it is less affected by the magnetic field generated when the coil 26 is energized. Therefore, the rotation angle detection accuracy by the magnetic sensors 31 and 32 is improved. Further, since the bottom portion 52 of the magnetic induction member 501 abuts against and is fixed to the end face 42 of the rotor core 41, a separate member for supporting the magnetic induction member is not required, and the number of parts and the cost are reduced.

[0029] The axially extending portion 55p of the magnetic induction member 501 is formed in a polygonal column shape having the same number of side faces as the number of rotor magnets 48. The polygonal column-shaped axially extending portion 55p is easy to manufacture by press working or the like. In the rotor 40 of the present embodiment having eight rotor magnets 48, the axially extending portion 55p is formed in an octagonal column shape. Substantially, the axially extending portion 55p is formed in a regular octagonal column shape in which the lengths of the respective sides are equal and the central angles of the respective sides are 45°. A flat plate portion forming one side face of the octagonal column in the axially extending portion 55p is referred to as a "unit plate of the axially extending portion 55p". Each unit plate of the axially extending portion 55p is arranged along the long side of the end face of the rotor magnet 48.

[0030] At the bottom 52, a plurality of inter-pole slits 54 are formed between adjacent rotor magnets 48 in the circumferential direction. Also, in the axially extending portion 55p, a plurality of inter-pole slits 56 are formed between adjacent rotor magnets 48 in the circumferential direction. By forming the inter-pole slits 56 from the upper end to the lower end of the axially extending portion 55p, the unit plates are arranged separately from each other. The inter-pole slits 54 and 56 are formed along the radiation centered on the rotation axis O. As a result, the leakage magnetic flux between the magnetic poles with different polarities adjacent in the circumferential direction is reduced, so that more magnetism can be induced in the magnetic sensors 31 and 32. Therefore, the rotational angle detection accuracy is improved.

[0031] In addition, in other embodiments, at least one of the inter-pole slits 54 at the bottom 52 or the inter-pole slits 56 at the axially extending portion 55p may be formed. By reducing the leakage magnetic flux between the magnetic poles in at least one of the bottom 52 or the axially extending portion 55p, more or less magnetism can be induced in the magnetic sensors 31 and 32.

[0032] Furthermore, in the first embodiment, the inter-pole slit 54 at the bottom 52 has a constant width radially inside the folding point F, and forms a widened portion 54w whose width widens as it moves away from the rotation axis O radially outside the folding point F. The minimum width of the inter-pole slit 54 is larger than the air gap δ between the rotor core 41 and the teeth 24. The inner wall of the widened portion 54w is parallel to the short side of the rotor magnet 48. The widened portion 54w in the 8-pole configuration spreads with an inclination of 22.5° on one side and 45° on both sides with respect to the center line M.

[0033] The circumferential width W1 of the unit plate of the axially extending portion 55p is a value obtained by adding the margins d×2 at both ends to the length a of the long side of the rotor magnet 48 (W1 = a + d×2). Since the circumferential width of the unit plate of the axially extending portion 55p is shorter than that in the second embodiment described later, the radial position of the axially extending portion 55p can be brought closer to the outer diameter of the rotor core 41, increasing the design freedom.

[0034] Further, a plurality of magnet slits 53 are formed in a portion of the bottom 52 that overlaps the end face of the rotor magnet 48. The end face of the rotor magnet 48 is exposed through the magnet slits 53. As a result, the leakage magnetic flux in the magnetic induction member 501 is reduced, so that more magnetism can be induced in the magnetic sensors 31 and 32. Therefore, the rotational angle detection accuracy is improved.

[0035] For the sake of illustration, the broken line representing the contour (hidden line) of the rotor magnet 48 and the solid line representing the contour of the magnet slit 53 are shown slightly shifted. In reality, it is preferable that they are formed in the same shape so that the contour of the magnet slit 53 coincides with the contour of the rotor magnet 48. However, the magnet slit 53 may be formed not necessarily in the entire portion overlapping the end face of the rotor magnet 48, but at least in a part of the portion overlapping the end face of the rotor magnet 48. Note that the broken lines shown at both ends in the longitudinal direction of the rotor magnet 48 represent voids for discharging the square holes.

[0036] Next, referring to FIGS. 5 and 6, the arrangement of the magnetic sensors 31 and 32 mounted on the substrate 33 will be described. In FIG. 5, the first magnetic sensor 31 and the second magnetic sensor 32 are schematically shown as circles, but do not show the actual shapes. With the first magnetic sensor 31 as a reference, the second magnetic sensor 32 is arranged at either the position indicated by the solid line or the position indicated by the broken line.

[0037] Here, a virtual plane including the center of the slot 25 in the circumferential direction of the stator 20 is defined as the slot center plane Ssc. Also, a virtual plane passing through the center of the rotor magnet 48 in the circumferential direction of the rotor 40 (hereinafter referred to as "rotor circumferential direction") is defined as the rotor magnet center plane Smc. In the configuration of 8 poles and 12 slots, the slot center plane Ssc appears every 30° of mechanical angle, and the rotor magnet center plane Smc appears every 45° of mechanical angle. At the rotor rotation position shown in FIG. 5, some of the slot center planes Ssc and some of the rotor magnet center planes Smc coincide.

[0038] In the circumferential direction of the stator 20, the first magnetic sensor 31 and the second magnetic sensor 32 are each arranged across the slot center plane Ssc. Preferably, they are arranged such that the circumferential centers of the magnetic sensors 31 and 32 are on the slot center plane Ssc. As a result, the circumferential distance between the magnetic sensors 31 and 32 and the coil 26 increases, so the magnetic distortion induced in the magnetic sensors 31 and 32 decreases, and the rotational angle detection accuracy improves.

[0039] Regarding the relative arrangement of the magnetic sensors 31 and 32, the second magnetic sensor 32 is arranged at a position with an electrical angle of 120° with respect to the first magnetic sensor 31. In the case of 8 magnetic poles, that is, 4 pole pairs, a mechanical angle of 90° (= 360° / 4) corresponds to an electrical angle of 360°, and an electrical angle of 120° corresponds to a mechanical angle of 30°. The positive and negative directions of the electrical angle are arbitrarily defined, and the second magnetic sensor 32 may be arranged on either the clockwise or counterclockwise side with respect to the first magnetic sensor 31. Also, the second magnetic sensor 32 may be arranged at a position with an electrical angle of 240°, that is, a mechanical angle of 60°, with respect to the first magnetic sensor 31.

[0040] In a brushless motor in which a three-phase current is applied to the coil 26, a 3nth harmonic component (n is an integer) is superimposed on the fundamental wave of the sensor signals of the magnetic sensors 31 and 32. Therefore, by taking the difference between the sensor signals of the two magnetic sensors 31 and 32 whose phases are shifted by 120° or 240° in the electrical angle, the 3nth harmonic component can be canceled. This technique is disclosed, for example, in Japanese Patent Application Laid-Open No. 2019-158374. Also, even when noise enters the signal lines from the magnetic sensors 31 and 32 to the signal processing device, the line noise can be reduced by taking the difference between the two sensor signals.

[0041] Fig. 6 shows an axial schematic cross-section at the rotor magnet center plane Smc. The first magnetic sensor 31 is shown in the following axial schematic cross-sectional views and is described as "magnetic sensor 31" in the description of the specification. However, since the magnetic sensors 31 and 32 are arranged on the same circumference centered on the rotation axis O, the same applies to the second magnetic sensor 32.

[0042] In the central plane Smc of the rotor magnet, the axial extension 55p has the shortest distance from the rotation axis O. In other words, the axial extension 55p is located most radially inward. At this position, the center Cs of the magnetic sensor 31 is arranged on the "opposite side to the stator 20" in the radial direction of the rotor (hereinafter referred to as the "rotor radial direction") with respect to the position Ex of the axial extension 55p of the magnetic induction member 501. In an inner rotor type motor, the center Cs of the magnetic sensor 31 is arranged radially inward with respect to the position Ex of the axial extension 55p.

[0043] By distancing the magnetic sensor 31 from the coil 26, it becomes difficult for the magnetic sensor 31 to be affected by the magnetic field generated when the coil 26 is energized. Therefore, the magnetic distortion induced in the magnetic sensor 31 is reduced, and the rotation angle detection accuracy is improved. Note that if the magnetic sensor 31 is brought too close to the radially inner side, the magnetic field from the axial extension 55p cannot be detected. Therefore, it is preferable that the magnetic sensor 31 is arranged at an optimal position where it can detect the magnetic field without being affected by the coil 26 as much as possible.

[0044] As described above, the brushless motor 101 of the first embodiment includes the magnetic induction member 501 that induces the magnetism of the rotor magnet 48 to the magnetic sensors 31 and 32, thereby reducing the influence of magnetic distortion due to the magnetic field of the coil 26 and improving the rotation angle detection accuracy.

[0045] In addition, since the magnetic induction member 501 has the axial extension 55p, the degree of freedom in the axial position of the magnetic sensors 31 and 32 is improved, and a surface mount type magnetic sensor can be used. Fig. 7 shows the magnetic sensor mounting structure of the brushless motor 109 of the comparative example without using the magnetic induction member. In the comparative example, the magnetic sensor 39 is inserted and mounted on the substrate 33 via the holder 38 which is a support member. The number of parts of the holder 38 increases, the assembly man-hours are increased, and the mounting positions of the magnetic sensors 39 also vary.

[0046] In the first embodiment compared with the comparative example, by using a surface-mounted magnetic sensor, the number of components and the cost are reduced, the mounting on the substrate 33 becomes easy, and the variation in the mounting positions of the magnetic sensors 31 and 32 is also suppressed. Therefore, it is advantageous in terms of rotation angle detection accuracy and cost.

[0047] Subsequently, for a plurality of embodiments in which the shape of the magnetic induction member, the arrangement of the magnetic sensors, etc. are different from those in the first embodiment, the differences mainly from the first embodiment will be mainly described. The code of the brushless motor in each embodiment is assigned the embodiment number at the third digit following "10", and the code of the magnetic induction member is assigned the embodiment number at the third digit following "50". The same codes are assigned to the substantially same configurations as those in the first embodiment in the plurality of embodiments, and the description thereof is omitted.

[0048] (Second Embodiment) FIG. 8 shows a schematic plan view of a brushless motor 102 according to the second embodiment. The magnetic induction member 502 of the second embodiment has no widened portion 54w in the inter-pole slit 54 at the bottom 52 compared with the first embodiment, and the inter-pole slit 54 is formed in a straight shape with a constant width. Therefore, the circumferential width W2 of the unit plate of the axial extension portion 55p in the second embodiment is larger than the circumferential width W1 of the unit plate of the axial extension portion 55p in the first embodiment (W2>W1). In the second embodiment, the processing of the inter-pole slit 54 becomes simpler than in the first embodiment.

[0049] (Third Embodiment) FIG. 9 shows a schematic plan view of a brushless motor 103 according to the third embodiment. The magnetic induction member 503 of the third embodiment has no magnet slit 53 formed in the bottom 52 compared with the first embodiment. The rotor magnet 48 hidden under the bottom 52 is shown by a dashed line. The magnetism of the rotor magnet 48 is transmitted to the bottom 52 formed of a magnetic material, and is induced from the bottom 52 to the magnetic sensors 31 and 32 through the air or the axial extension portion 55p. For example, when the plate thickness of the bottom 52 is thin and the leakage magnetic flux at the bottom 52 is small, such a configuration may be adopted.

[0050] (Fourth Embodiment) FIG. 10 and FIG. 11 show a schematic plan view and an axial-direction schematic cross-sectional view of a brushless motor 104 according to a fourth embodiment. The magnetic induction member 504 of the fourth embodiment has a bottom portion 52 and a columnar axially extending portion 55c. Similar to FIG. 6, FIG. 11 shows a cross-section at the rotor magnet center plane Smc in the rotor circumferential direction. Since the axially extending portion 55c is columnar, regardless of the position in the rotor circumferential direction, the position Ex of the axially extending portion 55c is constant. The center Cs of the magnetic sensor 31 is arranged on the "opposite side to the stator 20" in the rotor radial direction with respect to the position Ex of the axially extending portion 55c of the magnetic induction member 504. Therefore, similar to the first embodiment, the influence of the magnetic field of the coil 26 on the magnetic sensor 31 can be reduced, and the rotational angle detection accuracy is improved.

[0051] In the example of FIG. 10, a magnet slit 53 is formed in the bottom portion 52, but the inter-pole slit 54 in the bottom portion 52 and the inter-pole slit 56 in the axially extending portion 55c are not formed. In addition to this example, in a magnetic induction member having a columnar axially extending portion 55c, variations can be set according to the presence or absence of the magnet slit 53 or the inter-pole slits 54 and 56.

[0052] (Fifth Embodiment) FIG. 12 and FIG. 13 show a schematic plan view and a circumferential-direction development view of a brushless motor 105 according to a fifth embodiment. In the fifth embodiment compared to the fourth embodiment, an inter-pole slit 54 is formed in the bottom portion 52 of the magnetic induction member 505, and an inter-pole slit 56 is formed in the axially extending portion 55c. The inter-pole slit 56 in the axially extending portion 55c is not open at the upper end, and the upper portion is connected by a connecting portion 565.

[0053] In the fifth embodiment, similar to the first to third embodiments, the leakage magnetic flux between adjacent rotor magnets 48 is reduced by the inter-pole slits 54 and 56, and more magnetism can be induced to the magnetic sensors 31 and 32. Also, by connecting the upper portion of the inter-pole slit 56, although the leakage magnetic flux reduction effect is somewhat sacrificed, the deformation of the axially extending portion 55c during press working or assembly is suppressed, and the workability is improved.

[0054] (Sixth Embodiment) FIG. 14 shows an axial cross-sectional view of the brushless motor 106 according to the sixth embodiment. In the sixth embodiment compared to the first embodiment shown in FIG. 6, at the rotor magnet center plane Smc, the center Cs of the magnetic sensor 31 is arranged on the stator 20 side in the rotor radial direction with respect to the position Ex of the axial extension 55p of the magnetic induction member 506. In an inner rotor type motor, the center Cs of the magnetic sensor 31 is arranged radially outside with respect to the position Ex of the axial extension 55p. For example, when the axial distance between the coil 26 and the magnetic sensor 31 is relatively large and the magnetic sensor 31 is not easily affected by the magnetism of the coil 26, it may be configured in this way.

[0055] (Other Embodiments) (a) FIGS. 15 and 16 show other forms regarding the shape of the magnetic induction member. FIGS. 15 and 16 illustrate a cylindrical axial extension 55c. Also, not limited to the illustrated form, it may be formed of a single part or may be configured by combining a plurality of parts.

[0056] In the brushless motor 107 of the other embodiment (1) shown in FIG. 15, the magnetic induction member 507 is fixed to the rotor core 41 by caulking a protrusion 52c provided on the bottom 52 into a recess 41p formed on the surface of the rotor core 41. Therefore, the inner edge of the bottom 52 does not have to contact the outer periphery of the shaft 14. The magnetic induction member 507 further has a radial extension 57 that extends radially from the upper end of the axial extension 55c toward the magnetic sensor 31.

[0057] (b) In the brushless motor 108 of the other embodiment (2) shown in FIG. 16, the magnetic induction member 508 has a second axial extension 58 in addition to the axial extension 55c. The second axial extension 58 stands upright from the bottom 52 inside the radial direction of the rotor magnet 48. The magnetism of the rotor magnet 48 is induced to the magnetic sensor 31 via the two axial extensions 55c and 58. The magnetic induction member 508 is formed by welding, for example, two types of press parts having an L-shaped axial cross-section.

[0058] (c) The axial extension portions 55p and 55c are not necessarily erected perpendicularly from the bottom 52, i.e., parallel to the shaft 14 as shown in each axial cross-sectional view, and may be erected inclined with respect to the shaft 14.

[0059] (d) In addition to the 8-pole 12-slot example shown in the above embodiment, the number of poles and slots of the brushless motor may be any number. Also, it may be applied to a polyphase motor other than a three-phase motor. When it is desired to cancel kth harmonic components other than the third harmonic component superimposed on the detection signals of the magnetic sensors 31 and 32, the two magnetic sensors 31 and 32 are preferably arranged at positions that are multiples of the electrical angle (360 / k)°.

[0060] (e) In cases where the superimposition of the 3nth harmonic component is allowed, etc., a configuration including only one magnetic sensor 31 may be used. Also, in order to enhance the reliability against failures of the magnetic sensors, three or more magnetic sensors may be provided redundantly.

[0061] (f) The brushless motor of the present invention is not limited to an inner rotor type, and is also applicable to an outer rotor type motor. Regarding the positional relationship in the rotor radial direction between the center Cs of the magnetic sensor and the axial extension portions 55p and 55c in the rotor magnet center plane Smc (see FIGS. 6, 14, etc.), in an outer rotor type motor, the radially inner side corresponds to the stator side, and the radially outer side corresponds to the "side opposite to the stator".

[0062] As described above, the present invention is not limited to such embodiments, and can be implemented in various forms without departing from the spirit thereof.

[0063] The disclosure of "The brushless motor, wherein a plurality of inter-pole slits (54, 56) are formed between the rotor magnets adjacent to each other in the circumferential direction at at least one of the bottom portion or the axial extension portion of the magnetic induction member." may be combined with the disclosure of any brushless motor described previously.

[0064] The disclosure of "The brushless motor, wherein a plurality of magnet slits (53) are formed in at least a part of a portion overlapping with an end face of the rotor magnet at the bottom" may be combined with the disclosure of any brushless motor described previously.

[0065] The disclosure of "The brushless motor, wherein an axially extending portion of the magnetic induction member is formed in a polygonal columnar shape having a side surface equal in number to the number of the rotor magnets" may be combined with the disclosure of any brushless motor described previously.

[0066] The disclosure of "The brushless motor, wherein at least one of the magnetic sensors is arranged across a virtual plane (Ssc) including the center of the slot in the circumferential direction of the stator", and the disclosure of "In a brushless motor in which a three-phase current is applied to a coil of the stator, a plurality of the magnetic sensors are provided, and a second magnetic sensor (32) is arranged at a position of an electrical angle of 120° or 240° with respect to a first magnetic sensor (31)" may be combined with the disclosure of "In a brushless motor, when a circumferential direction of the rotor is defined as a rotor circumferential direction and a radial direction of the rotor is defined as a rotor radial direction, in a virtual plane (Smc) passing through the center of the rotor magnet in the rotor circumferential direction, a center (Cs) of the magnetic sensor is arranged on a side opposite to the stator in the rotor radial direction with respect to the axially extending portion of the magnetic induction member".

Description of Reference Numerals

[0067] 101 to 108... Brushless motors, 14... Shaft 20... Stator, 24... Teeth, 25... Slots 26... Coil 31... (First) Magnetic sensor, 32... (Second) Magnetic sensor 33... Substrate 40... Rotor, 48... Rotor magnet 501 to 508... magnetic induction members, 52... bottom, 55p, 55c... axially extending portions.

Claims

1. A stator (20) in which a coil (26) is wound around a plurality of teeth (24) arranged in the circumferential direction, and a slot (25) is formed between adjacent teeth; A rotor core (41) and a plurality of rotor magnets (48) that form a plurality of magnetic poles with alternating polarities in the circumferential direction of the rotor core. The rotor (40) rotates about a shaft (14) by a rotating magnetic field generated by energizing the coil; One or more magnetic sensors (31, 32) provided on a substrate (33) fixed to the stator at a position axially away from the end face of the rotor core, and detecting the rotation angle of the rotor based on the change in magnetism of the rotor magnet; A magnetic induction member (501-508) having a bottom (52) that abuts against the end face of the rotor core and axial extension portions (55p, 55c) erected from the bottom toward the magnetic sensor, and guiding the magnetism of the rotor magnet to the magnetic sensor; A brushless motor comprising the above.

2. The brushless motor according to claim 1, wherein the magnetic induction member is integrally formed with the bottom and the axial extension portion.

3. The brushless motor according to claim 1, wherein a plurality of inter-pole slits (54, 56) are formed between the rotor magnets adjacent to each other in the circumferential direction in at least one of the bottom or the axial extension portion of the magnetic induction member.

4. The brushless motor according to claim 1, wherein a plurality of magnet slits (53) are formed in at least a part of the portion of the bottom that overlaps the end face of the rotor magnet.

5. The brushless motor according to claim 1, wherein the axial extension portion of the magnetic induction member is formed in a polygonal column shape having a side surface equal to the number of the rotor magnets.

6. When the circumferential direction of the rotor is defined as the rotor circumferential direction and the radial direction of the rotor is defined as the rotor radial direction, In a virtual plane (Smc) passing through the center of the rotor magnet in the rotor circumferential direction, the center (Cs) of the magnetic sensor is arranged on the opposite side of the stator in the rotor radial direction with respect to the axial extension of the magnetic induction member. The brushless motor according to any one of claims 1 to 5.

7. At least one of the magnetic sensors is arranged across a virtual plane (Ssc) including the center of the slot in the circumferential direction of the stator. The brushless motor according to any one of claims 1 to 5.

8. In a brushless motor in which a three-phase current is applied to the coil of the stator, a plurality of the magnetic sensors are provided, and the second magnetic sensor (32) is arranged at a position of an electrical angle of 120° or 240° with respect to the first magnetic sensor (31). The brushless motor according to any one of claims 1 to 5.

Images